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USGS Mendenhall Postdoctoral  Research Fellowship Program

14-10. The Fate of Volcanic Ash in the Atmosphere: Eruption, Transport, and Removal Processes

We seek a postdoctoral candidate who collects and analyzes data from tephra deposits, dispersal models, or volcanic ash clouds to better understand how tephra is added to, removed from, and transported through the atmosphere during explosive eruptions.

The shutdown of European airspace in April 2010 during the eruption of Eyjafjallajökull volcano, Iceland, cost an estimated $5B and demonstrated that volcanic eruptions can affect areas thousands of kilometers from the source.  The United States contains more than 150 active volcanoes, mostly in Alaska.  Every day, aircraft carry about 300,000 passengers and millions of dollars of cargo near one or more of these volcanoes.  More than a dozen historically active U.S. volcanoes lie close enough to metropolitan areas to disrupt transportation, damage infrastructure and impact health from tephra fall.  Improved forecasting of areas affected by tephra is critical to minimizing economic loss, and is a goal of the USGS Natural Hazards Science Strategy (

Accurate forecasts of tephra hazards can build on three types of information: (1) understanding frequency, magnitude, and distribution of past tephra emissions at specific volcanoes, (2) monitoring volcanoes during unrest to detect the time of onset, plume height, and direction of tephra transport once an eruption has started, and (3) forecasting areas affected by tephra deposition during eruptions through numerical models and human judgment.  Tephra deposits from key U.S. volcanoes have long been studied, but many such studies including notably Mount St. Helens, were conducted before modern analytical techniques that better constrain age and eruptive processes.  In monitoring, the USGS has improved our capability through acquisition of a transportable Doppler weather radar.  We have also improved our forecasting capability through development of an advanced tephra transport model, Ash3d.  But incomplete understanding of key processes has limited model accuracy.  One such process is particle aggregation, in which ash particles clump together and fall out faster than predicted.  Aggregation accelerated ash removal during eruptions at Mount St. Helens in 1980 (through vapor-ash interactions) Kasatochi in 2008 (rain), Okmok in 2008 (eruption through a wet crater), and Redoubt in 2009 (formation of ice aggregates).  Rates and mechanisms of aggregation vary with atmospheric conditions and are insufficiently understood to be realistically incorporated into any tephra model.  Thus to date, no model simulation of a tephra deposit has been able match mapped observations without retrospective, ad hoc adjustments to grain-size distribution or particle-fall velocity.

This Opportunity aims to take advantage of deposits in the Cascade Range and Alaska, a strong USGS tephra modeling group, laboratories at Cascades and Alaska Volcano Observatories, and remote sensing expertise at Alaska Volcano Observatory. Ideal research topics will combine observations with experiments and models to forecast tephra distribution more accurately.  Potential research projects might include:

Available USGS datasets include satellite retrievals, radar, deposit maps, samples, and grain-size data from past eruptions.  Also available are NOAA model output on historical atmospheric conditions and wind fields extending back to the 1940s.

USGS laboratories in Anchorage and Vancouver are available with tephra processing equipment and scanning electron microscopes. Electron microprobes, FTIR, an ion probe, and other analytical facilities are available at other USGS locations.  Models available for this research can be run on any of several computers at the USGS.  The North Pacific typically experiences about one large eruption per year, offering a chance to collect data from an ongoing eruption.

The USGS works closely with the National Weather Service and the FAA to monitor and forecast tephra hazards during eruptions.  Since the 2010 eruption of Eyjafjallajökull, forecast accuracy has become a matter of concern well beyond the volcanological community.  The aviation community, for example, has begun to demand that forecasts indicate not only the location and extent of ash clouds, but also the ash concentration, so they can identify areas of “dilute” ash where flight is still possible.  Forecasting ash concentration requires real-time estimates of mass eruption rate, which are currently imprecise.  Moreover, no operational models include particle aggregation.  Hence during an eruption, current models cannot forecast concentration to an accuracy better than an order of magnitude, and are unable to predict the longevity of an ash cloud.  Understanding processes that control ash-cloud concentration is therefore both timely and societally relevant.

Proposed Duty Station: Vancouver, WA

Areas of Ph.D.: Geology, Geophysics, Meteorology, Applied Mathematics, or related fields (candidates holding a Ph.D. in other disciplines, but with extensive knowledge and skills relevant to the Research Opportunity may be considered).

Qualifications: Applicants must meet one of the following qualifications: Research Geologist, Research Geophysicist, Research Mathematician, Research Physicist.

(This type of research is performed by those who have backgrounds in the occupations stated above.  However, other titles may be applicable depending on the applicant’s background, education, and research proposal.  The final classification of theposition will be made by the Human Resources specialist).

Research Advisors:   Larry Mastin, (360) 993-8925,; David Schneider, (907) 250-7923,; James Vallance, (360) 993-8959,; Kristi Wallace, (907) 786-7109;

Human Resources Office Contact: Robert Hosinski, (916) 278-9397,

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U.S. Department of the Interior, U.S. Geological Survey
URL: Mastin.htm
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Last modified: 17:58:01 Tue 23 Jul 2013
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